The B Vitamins and Cognitive Health

B vitamins are crucial micronutrients that are vital for preserving cognitive health due to their role in one carbon metabolism, mitochondrial energy production, and maintaining the structure of neurons. Folate, vitamin B6, and vitamin B12 are necessary for the regulation of methylation processes by aiding in the demethylation of homocysteine and the production of S-adenosylmethionine, the universal methyl donor required for epigenetic alterations of DNA, RNA, and histones. A lack of these vitamins results in hyperhomocysteinemia, reduced methylation capacity, and greater neuronal vulnerability, all of which contribute to cognitive decline and increase the risk of neurodegenerative diseases. In addition to methylation, B vitamins serve as essential cofactors in the mitochondrial enzymatic processes that create ATP, facilitate neurotransmitter synthesis, and control oxidative stress. Sufficient levels of B vitamins enhance neuronal survival by maintaining synaptic plasticity, stabilizing membrane phospholipids, and reducing neuroinflammation. Research from preclinical models and clinical cohort studies indicates a connection between inadequate B vitamin intake and accelerated cortical atrophy, memory decline, and heightened dementia risk. Trials on supplementation suggest possible advantages in decelerating cognitive decline, although results can be affected by genetic variations, initial nutritional status, and differences in study design. This chapter brings together mechanistic and translational evidence to demonstrate how B vitamins synchronize methylation, mitochondrial functionality, and neuronal health, highlighting their potential as a cost-effective and accessible approach to counteracting age-related cognitive decline and the burden of neurodegeneration.